Effects of alkyl side-chain length on binding with bovine serum albumin, cytotoxicity, and antibacterial properties of 1-alkyl-3-methylimidazolium dicyanamide ionic liquids

Abstract

Abstract In this study, the behavior of 1-alkyl-3-methylimidazolium dicyanamide ionic liquids (ILs) with ethyl, butyl, hexyl, octyl, and decyl side-chains was evaluated to gain a deeper insight into the potential hazards posed by ILs to the environment and organisms. The effects of the alkyl side-chain length on the interactions between the ILs and bovine serum albumin (BSA), the cytotoxicity and antibacterial performance of the ILs was evaluated. The BSA binding ability of the ILs increased with increasing alkyl side-chain length, and the binding constants of the ILs increased from 1.80 L/mol for 1-ethyl-3-methylimidazolium dicyanamide to 196 L/mol for 1-decyl-3-methylimidazolium dicyanamide. IL binding with BSA was a spontaneous process initiated by hydrophobic forces. This was confirmed using circular dichroism spectra, dynamic light scattering measurements and molecular docking simulations. The results of the cytotoxicity and antimicrobial activity of ILs demonstrated that the increase in alkyl side-chain length increased IL toxicity. The effects of the alkyl side-chain length of 1-alkyl-3-methylimidazolium tetrafluoroborate ILs on the interactions between ILs and BSA and cytotoxicity of the ILs were also evaluated. Furthermore, we demonstrated that tetrafluoroborate-based ILs were more toxic than dicyanamide-based ILs. Herein, we thoroughly describe the effects of the alkyl side-chain length on the properties of ILs and provide background information for future studies on the properties of carbon dots fabricated using ILs as precursors.